So far, yes. Probably the best description would be an end of a chapter.

Trine 4 is completely separate, which makes sense. It's a 2.5D game again, instead of 3D.

No idea if Trine 3 story will be continued. I'd like that, but there is no info.

Trine 3 game ends the characters saying that they will go one more last adventure.

they ran out of money, so only 1 chapter out of 3 and never revisited after poor reviews and sales. Which is a shame.

Originally posted by Menkerot:

they ran out of money, so only 1 chapter out of 3 and never revisited after poor reviews and sales. Which is a shame.

I didn't get the joke about running out of money. But the money was found for other games, including part 4 and 5.

I did notice that Trine 5 has some story references here and there to some of this game's plot elements such as a brief mention of Trine's sister at one point, as well as some that we never got to experience within the game itself.

Also, spoilers for Trine 4:
If you find all the keys in every level, you can unlock a special door in the main menu that leads to a secret room where you'll find pages of the Trine 3 storybook ripped out with Zoya mentioning that the dog ate the rest of the pages after their adventures in Redwood Forest, a reference to where this game abruptly ended.

So aside from brief references to Trine 3 (and even 1&2) in future games, those stories don't really connect with this one as they still felt more like new stories in the same universe if that makes sense. They still don't fill in the gaps between where the game ends and where the actual story itself was supposed to end, however.